EXOS MLAG/LACP question / clarification

[Frank]

I'm trying to get a clearer understanding of when to use MLAG with LACP and when not. I did read the note in https://extremeportal.force.com/ExtrArticleDetail?an=000079895 that reads "if the downstream device (e.g. switch, server, etc..) is using LACP LAG sharing on its ports, it will be necessary to enable LACP LAG on the MLAG ports", but I'm still a little fuzzy - probably because I don't understand the "black magic" fully.

Here's my layout - we're running EXOS 16.x:
ISC (ports 1:24/2:24) BD8800-1 ==== BD8800-2 1:1| 2:1\ 1:1/ |2:1 | \ / | | X | | / \ | 23| 24/ 23\ |24 Switch-1 Switch-2 5| 5| | | | | Server (Linux or Microsoft) with LACP share

Shared port group between the BD8800s for the ISC (enable sharing 1:24 grouping 1:24,2:24)
1-port shared "port group" to Switch-1 on the 8800 (enable sharing 1:1 grouping 1:1)
Same to Switch 2 (enable sharing 2:1 grouping 2:1)
Shared port group on Switch-1/2 to the BD8800s (sharing 23 grouping 23,24)
Single-port share-group on Switch-1 and Switch-2 on the port 5 to the server

mlag: enable mlag port 1:1 peer "8800-1/2" id 123 (on the 8800s)

On top of that: The BD8800s are the "default gateway" in a VRRP configuration for the vlan that the attached server is in (in case it matters)

Question 1:
In the scenario above, what shares on which switches/shares would have to be done with LACP - for instance "enable sharing X grouping ... L3_L4 LACP" (since I'd like to use L3_L4 on the server side)?

Question 2:
If I were to add an ISC link between Switch-1 and Switch-2, would the only LACP share configuration be on Switch-1/2 (and not on BDs)?

Question 3:
Are there any advantages/disadvantages to using "LACP" as opposed to not using it and going with Extreme's "pure purple magic"?


Thank you for looking at this!

[Frank]

Thank you all very much!
I think I (finally) got it 🙂
Frank

[Tomasz · Accepted solution]

Hi Frank,

Just to make sure, do you have the 2-tier MLAG deployed already there, or is it just a concept for more links and higher redundancy at the moment?

Every MLAG instance is a unique thing. You could do only BDs-to-Switches MLAGs, one for each Switch#, with all (or some set of) VLANs traversing north-south and thru ISC. Having two-tier MLAG (the former and another one from Switches to BD perspective) gives you complete MLAG-based redundancy that is possible with two pairs of devices on each tier. I believe it's good to have 2-tier MLAG in place with your scenario.

If I understood your concern properly, your Switch 1 and 2 -based MLAG for the Server can be treated independently from two-tier (and MLAG to any other server would be a separate MLAG instance as well, they can utilize the same physical links for ISC though). You can have 2-tier MLAG on top and not work the same way with your server links, you can have MLAG for servers link redundancy without 2-tier above, or you can have both.
Full MLAG in your diagram would mean to have two MLAG configurations in 2-tier and third one on server access side, 3 MLAG 'deployments' total. Make sure to pass the right VLANs in all of the aggregated links and the ISCs.

If you take a look at EXOS User Guide chapter 6 (https://www.extremenetworks.com/support/documentation/extremexos-software-22-5/) you may find configuration guidelines and an example that is relevant to your diagram as well, please see pages 254-257 (the last page shows your example).

Hope that helps,
Tomasz

[Frank]

I think the documentation just hit me over the head:

You must add the ISC to every VLAN that has an MLAG link as a member port

For my config, I'll take that to mean "Full two-tier MLAG - or things won't work right"

[Frank]

Thomasz, thank you for your detailed and insightful answer!

Final (hopefully) question: Since I'm "only" building an ISC/MLAG link between Switch-1 and Switch-2 to accommodate LACP to a device attached to Switch-1 and Switch-2, do I have to go full-blown two-tier MLAG, or can I treat it as a separate mlag, just for "port-5". I admit, I haven't fully thought it through, but if I need to build a full two-tier MLAG, I'll have to have a real service window when I put ports 1:1/1:2 on the BD8800s in a share.
What I mean is: create an ISC, mlag port(s) 5, but don't tag port 5's vlan (data-vlan) to the ISC port. In my case, "port 5" is the only port in that vlan on switch1/2 (except for the 23/24 share going up to the BDs), anything else that would be in that vlan is on other switches that are attached to the BDs

If I can get away with a "this is a separate mlag", then things become simpler from a scheduling aspect.

I have a nagging feeling that the "separate mlag" option, where I just mlag only for the LACP links is going to trip me up in the future when I see "ISC, oh, just handle it like everywhere else and tag all the vlans through it as well", so I realize I really should do full-two-tier at some point "soon".